Halides reagents

Organomagnesium halide reagents RMgX (RX = CjH,Br, i-PrBr, n-BuBr, PhBr) react in toluene-ether with (t7 -Cp)2MoH2 to form compounds II, in which each molecule contains four Mo—Mg bonds " . When II is dissolved in THF a red solution is formed, which after concentration yields orange crystals of III. Compound III is monomeric with a Mo—Mg bond of length 273.2 pm, consistent for Mo as a one-electron donor. 

The acticm of acids, halogens and halogen-releasing agents, as well as phosphorus, sulphur and other inorganic halide reagents was carefully investigated. OYP cal laboratory parameters in the treatment of impure trifluralin with various acids follow. 

Halohydrin dehalogenase activity was determined by monitoring halide liberation at 30 °C in tris-S04 buffer (50 mM, pH 8.0) containing 5 mM 1,3-dichloropropanol or 1,3-dibromopropanol as the substrate. All buffers used for activity assay were prepared with bidest water. From the incubation mixture, 0.5 ml samples were taken and mixed with 1.6 ml of H2O, 0.2 ml or halide reagent 1 and 0.2 ml of halide reagent II. Absorbances were read at 460 nm. A calibration curve of 0-1 mM of chloride or bromide was used to calculate the concentration of halide. The extinctions at 460 nm should be below 0.4 (for chloride) or 0.8 (for bromide). 

In CHEC-II(1996) only one example of N-alkylation of a cinnolin-4(l//)-one is given <1996CHEC-II(6)1>. Nowadays, N-alkylation of pyridazinones is a quite general reaction. In most cases alkylations are achieved by a nucleophilic substitution reaction of the deprotonated azinone on alkyl halides and exceptionally also on aryl halides. Reagents other than halides are also used. 

Uneyama has described some interesting reactions of the N-aryl imines of ethyl trifluoropyruvate. Tandem alkylation/defluorination occurred (Eq. 97) upon exposure to diethylzinc, via attack at nitrogen and SN2 displacement of fluoride anion [279]. Interestingly, an alkylzinc halide reagent attacked regioselec-tively at carbon, perhaps the more expected outcome. 

Several further examples have been reported of the replacement of hydroxyl (or oxo) substituents in 1,10-phenanthrolines by halogens with phosphorus halide reagents.38 96 196,198,213 213,219,293,340-342 4-Ethoxy-7-hydroxy-l,10-phenanthroline reacts normally with diazomethane to afford 4-ethoxy-7-methoxy-1,10-phenanthroline.203... 

In the example given in Scheme 3j18 the primary step in the Reformatsky reaction is the addition of the halide reagent and zinc to the protected peptide 12 in THF hydrolysis of the intermediate formed results in the corresponding difluoroalkyl alcohol 13. Since compound... 

The nature of the zinc (dust, foil, or shots) is important for the success of the formation of an organozinc halide by oxidative addition. Usually, the use of zinc dust (-325 mesh) from Aldrich or Riedel de Haen gives the best results. In some cases, such as for the preparation of allylic zinc halide reagents,22,28 iodomethylzinc iodide,65 or benzylic zinc halides,66 the use of zinc foil (0.1 mm or 0.25 mm thick, Aldrich or Merck) may be advantageous or even essential. 

The insertion tendency decreases in the order r-BuLi > 5-BuLi > n-BuLi > PhLi > MeLi. These insertions can be carried out by using lithium alkanides, alkenides, alkynides, and aromatic or heterocyclic lithium compounds. The lithiation should not be carried out by using alkyl halides, because the lithium tellnrolates that are formed in the reaction may react with the alkyl halide reagent to produce organyl alkyl tellurides. ... 

Allyliczinc halides reagents have been prepared from sterically hindered homoallylic alcohols, using a novel fragmentation reaction of the corresponding zinc aUcoxide (Scheme 6). The interest of this reaction resides in the absence of the Wurtz homocoupling product, usually present in high proportion when the direct reaction of zinc with allylic halides is used. 

Among organomagnesium halide reagents, only Mg(I)Me and Mg(Br)CH2-Ph react with (>/ -Cp)2TiCl2 to give dialkylated products the route usually leads to... 

Table 1. Reactions of Cyclopentadienyltitanium Halides with Allylmagnesium Halide Reagents, RMgX... 

The reaction of organolithiums or organomagnesium halide reagents with gold halides proceeds similarly to the copper halides in a 1 1 ratio. Their phosphine complexes can be isolated and characterized. In a 2 1 ratio, the transmetallation reaction is followed by ate complexation to form organoaurate complexes ... 

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